Extended range diving is a joint effort by Scuba Schools International and Mares to encourage students to use their current recreational equipment to explore the possibilities beyond the range of recreational diving inherent in the use of a single tank of air. Each of the systems with which you are familiar can be enhanced, extended and/or replaced to allow divers to go deeper, farther and stay longer.
Buoyancy systems can progress from a recreational BCD with a single back-mounted tank to the addition of a smaller, second tank of air to the purchase of a new buoyancy system that can support two back-mounted tanks of gas with one or two side gas bottles. That progression suggests moving from the use of a single regulator to multiple regulators - one for each tank.
There are lights and reels and cords and fasteners and clips and screws and bands and bungee cords and straps and pockets to add - the list can be endless. It can also be very short by adding one element at a time.
Just think...what's down there? How long can I stay to look? How will it expand my knowledge? How will it change my life?